In the laboratory, a student dilutes 26.8 mL of a 7.23 M hydrobromic acid solution to a total volume of 150.0 mL. What is the concentration of the diluted solution?

Question

Concentration = ?  M

Answer 1

A very simple method for this is to use V1M1 = V2M2 where...

V1 = initial volume = 26.8 ml

M1 = initial molarity = 7.23 M

V2 = final volume = 150 ml

M2 = final molarity = ?

(26.8 ml)(7.23 M) = (150 ml)(x M)

x = 1.29 M

Answer 2

First, we need to find how many mol of HBr in 26,8 mL solution

26,8 mL=0.0268 L

7,23 M solution means that 1 L of solution 7.23 mol of HBr

so, 7,23 mol x 0.0268L = 0.194 mol/L

When the student added water, the solution was 150mL= 0.150 L

but HBr 0.194 mol is still there

just the concentration changed

so, M =0.194 mol/L / 0.150 L = 1.29 M